Hi, thanks for the reply!
By using a custom particle, do you mean when you click the 'Sprite' button? I managed to use it, and actually it loaded a particle from the folders within the program only through using the Sprite button this time, so there's a way to circumvent it at least.
Also, is it possible to reroute where the renders are being exported to? sometimes they won't show in the default folder for some reason, so I'm wanting to try and make a folder to tidy things up, and maybe see if I can watch for which ones are/aren't exporting.